Tyrosine kinases play an essential role in the regulation of cell signaling and cell proliferation by phosphorylating tyrosine residues of peptides and proteins. Inappropriate activation of tyrosine kinases is known to be involved in a variety of disease states, including immunologic and oncologic disorders.
It has been well established that T cells play an important role in regulating the immune response (F. Powrie and R. L. Coffman, Immunol. Today, 1993, 14, 270). Activation of T cells is often the initiating event in many inflammatory and autoimmune diseases. In addition to their role in immune surveillance, T cells can become autoreactive by recognizing self-antigens and thereby cause autoimmune disease such as rheumatoid arthritis and inflammatory bowel disease.
The T cell receptor (TCR) is the antigen-specific component of the T cell and is activated when the receptor is engaged with foreign or self-antigenic peptides. When the TCR is activated a series of enzyme-mediated signal transduction cascades is initiated which results in the production of pro-inflammatory cytokines such as interlukin-2 (IL-2). The release of IL-2 is critically important since this lymphokine is required for T-lymphocyte proliferation, differentiation, and effector function. Clinical studies have shown that interference with IL-2 activity effectively suppresses immune response in vivo (T. A. Waldmann, Immunol. Today, 1993, 14, 270). Accordingly, agents which inhibit T-lymphocyte activation and subsequent IL-2 production, or block the activity of IL-2 are therapeutically useful for selectively suppressing immune response in a patient in need of such immunosuppression.
The eight members of the src family of tyrosine kinases are src, lck, fyn, lyn, hck, fgr, blk and yes (J. B. Bolen, J. S. Brugge, Ann. Rev. Immunol., 1997, 15, 371). These can be divided into 2 groups based on their pattern of tissue expression. Src, fyn and yes have a broad distribution while expression of lck, lyn, hck, fgr, and blk is largely limited to hemopoietic cells. The therapeutic effects of inhibiting kinases of the src family can be ascertained by linking functional defects seen in gene disruption studies in mice. Src(−/−) mice had severe abnormalities in bone remodeling. Inhibition of src may therefore be useful in treating osteoporosis. Lck(−/−) mice display a complete lack of CD4+ cells are unable to mount antigen-dependent immune responses.
A kinase of particular interest is p56lck, which is only expressed in T-cells. Within the TCR signal transduction cascade the tyrosine kinase p56lck is a required element to initiate the activation response from the TCR intracellular domains to other signaling proteins. For example, T cells which lack the p56lck protein are unable to signal through the T cell receptor (D. B. Straus and A. Weiss, Cell, 1992, 70, 585). Transfection of p56lck back into these cell lines restores TCR responsiveness. Also, it has been shown in mice that inactivation of the p56lck gene leads to lack of proper thymocyte development (T. J. Molina et al., Nature, 1992, 357, 161).
The conclusion drawn from these studies is that p56lck plays a crucial role in T cell maturation and antigen-induced T-cell activation. Therefore, an agent blocking p56lck would effectively block T cell function, act as an immunosuppressive agent and have potential utility in autoimmune diseases, for example rheumatoid arthritis, multiple sclerosis, lupus, transplant rejection and allergic diseases (J. H. Hanke et al., Inflamm. Res., 1995, 44, 357).
Inhibitors of other members of the src family of non-receptor tyrosine kinases are also useful for treating various disease states. Src is present in osteoclasts, and is important in bone remodeling. For example, inactivation of p60src diminishes bone resorption by osteoclasts (P. Soriano et al., Cell 1991, 64, 693, B. F. Boyce et al. J. Clin. Invest 1992, 90, 1622), it is therefore possible that inhibitors of the kinase activity of p60src are useful in the treatment of osteoporosis, Paget's disease and inflammation of bones and joints.
Src kinases have been found to be activated in tumors, including breast and colon cancers, melanoma and sarcoma. For example, a number of primary tumors and tumor cell lines from patients with breast cancer, colon cancer, melanoma and sarcoma have been shown to have elevated src kinase activity, and activating src mutations are seen in some advanced colon cancers. Inhibitors of src kinase had significant antiproliferative activity against cancer cell lines (M. M. Moasser et al., Cancer Res., 1999, 59, 6145) and inhibited the transformation of cells to an oncogenic phenotype (R. Karni et al., Oncogene, 1999, 18, 4654) suggesting that src kinase inhibitors may be useful anti-cancer agents.
Src inhibitors have also been reported to be effective in an animal model of cerebral ischemia (R. Paul et al. Nature Medicine 2001, 7, 222), suggesting that src kinase inhibitors may thus be useful in treating conditions involving cerebral ischemia. For example, src kinase inhibitors may be useful in reducing brain damage following stroke.
In addition, src family kinases participate in signal transduction in several cell types. For example, fyn, like lck, is involved in T-cell activation. Hck and fgr are involved in Fc gamma receptor mediated oxidative burst of neutrophils. Src and lyn are believed to be important in Fc epsilon induced degranulation of mast cells, and so may play a role in asthma and other allergic diseases. The kinase lyn is known to be involved in the cellular response to DNA damage induced by UV light (T. Hiwasa, FEBS Lett. 1999, 444, 173) or ionizing radiation (S. Kumar, J. Biol Chem, 1998, 273, 25654). Inhibitors of lyn kinase may thus be useful as potentiators in radiation therapy.
Platelet derived growth factor is a potent mitogen for smooth muscle cells. Its receptor (PDGFR) is a member of the receptor tyrosine kinase family (L. Claesson-Welsh, J. Biol Chem, 1994, 269, 32023). PDGF is involved in atherosclerosis and restenosis (K. E. Bornfeldt, Trends Cardiovasc. Med., 1996, 6, 143). In addition, receptor tyrosine kinases including PDGFR kinase have been implicated as contributing factors in cancer (A. Levitzki and A. Gazit, Science, 1995, 267, 1782) including ovarian (M. B. Dabrow et al., Gynecologic Oncology, 1998, 71, 29) and prostate (S. M. Sintich et al., Endocrinology, 1999, 140, 3411) cancers and glioblastoma (B. J. Silver, BioFactors, 1992 3, 217). Inhibitors of PDGFR kinase are thus useful in the treatment of fibrotic diseases, restenosis and PDGF-dependent tumors. Reports have appeared in the literature of agents that inhibit the kinase activity of p56lck kinase and thus inhibit T cell activation. These include the natural product lavendustin A, and analogs (M. S. Smyth, J. Med. Chem., 1993, 36, 3010), the natural product damnacanthal (C. R. Faltynek et al., Biochemistry, 1995, 34, 12404), and a 1-methoxy agroclavine isolated from a fungal extract (R. Padmanabha et al. Bioorganic and Med. Chem. Letters, 1998, 8, 569). Other inhibitors reported include WIN 61651 (J. Enzyme Inhibition, 1995, 9, 111) pyrazolopyrimidines PP1 and PP2 (Hanke et al. J. Biol Chem, 1996, 271, 695) and indanone and indandione derivatives (J. L. Bullington et al., Bioorganic and Med. Chem. Letters, 1998, 8, 2489).
A. P. Spader et al. (WO 98/54157, 1998) describe quinoline and quinoxaline compounds that inhibit p56lck and PDGFR kinase. Fused polycyclic 2-aminopyrimidine derivatives that inhibit p56lck are reported by J. M. Davis et al. (WO 98/28281, 1998). J. Das et al. claim a series of benzothiazole amides as inhibitors of lck and other src family kinases (WO 99/24035, 1999). Inhibitors of PDGFR kinase and src-family kinases were reviewed by H. D. H. Showalter, A. J. Kraker, Pharmacol. Ther., 1997, 76, 55. Several patents on inhibitors of lck are reviewed in P. M. Traxler, Exp. Opin. Ther. Patents, 1997, 7, 571, and P. M. Traxler, Exp. Opin. Ther. Patents, 1998, 8, 1599.
EP 322 746 A1 discloses heterocyclic lactam derivatives described as being useful as cardiotonic agents, antihypertensive agents and vasodilators.
Examples of tricyclic systems similar to formula (I) above are known, but not having the 2-amino substituents on the benzimidazole ring. See S. W. Schneller et al., J. Med. Chem., 1989, 32, 2247. Examples of tricyclic systems similar to formula (I) with a carbamate at the 2-position have been reported in S. Kumar et al., Indian J. Chem. 1981, 20B, 1068 and S. Agarwal et al., Z. Naturforsch. C, 1993, 48, 829.
The compounds of the present invention represent a novel structural class, which is distinct from previously reported tyrosine kinase inhibitors.